1. Field of the Invention
The present invention pertains to multi-touch input systems and methods, and more particularly to a mixture of chord keying, gesture recognition and touch typing techniques.
2. The Related Art
The primary use of chords, or simultaneous finger presses, within the data entry art has been in chord keying schemes that map each letter of the alphabet or even shorthand word parts to a different finger combination. This allows chord keyboards to have a reduced number of keys, often limited to a home row of keys. This in turn reduces finger travel and potentially speeds typing. Some schemes, like U.S. Pat. No. 5,281,966 to Walsh, adopt a mapping that is sensibly organized so as to be easy to learn and remember, while others, such as U.S. Pat. No. 5,642,108 to Gopher et al., emphasize long-term keying performance by assigning the most frequently entered letters of the alphabet to those finger combinations that are quickest and easiest to perform. In U.S. Pat. No. 5,808,567, McClound discloses a scheme for communicating with three-finger chords. In this system, a touch of the index finger on one of the nine regions of a small selector pad can be modified by thumb and/or middle finger presses on switch pads adjacent to the selector pad.
The recent development of multiple-touch sensitive surfaces that lack the restrictions of distinct mechanical keys warrants a reexamination of chording schemes. Direct adaptation of the chord keying schemes cited above to a multi-touch surface certainly seems feasible, but may not be desirable. U.S. Pat. No. 5,825,352 to Bisset et al. describes a touchpad with row and column electrodes that produces pointing in response to single finger motion and dragging in response to two finger motion. U.S. Pat. No. 6,107,997, Ure utilizes the touch sensor array of U.S. Pat. No. 5,194,862 and interprets single finger motions as pointing while interpreting various placements of a 2-finger chord on a grid as key entry. In U.S. application Ser. No. 09/236,513, however, Westerman and Elias take yet another approach, interpreting asynchronous touches on a multi-touch surface (MTS) as conventional single-finger typing while interpreting motions initiated by chords as pointing, clicking, and other gesture commands. We prefer this approach for the following reasons: learning a few new chords for graphical manipulation is much easier than learning a slew of new chords for typing the whole alphabet, and graphical manipulation seems a better use of chords in today's graphics intensive computing environment. In dictation situations where greater text entry speeds are needed than can be achieved with non-chordic keying, adopting a continuous speech recognition system for text entry is becoming more practical than learning a chord keying technique.
Non-chordic touch typing on surfaces that provide limited tactile feedback presents its own difficulties. If the typist is not careful, the hands or individual fingers tend to drift out of alignment with the key layout, or more particularly with the home row of keys where hands normally rest. Reaching for punctuation and modifier keys located on the periphery of QWERTY computer keyboard layouts exacerbates this drift. Though the Shift modifier key is not particularly far from the home row keys, the direction of pinky motion needed to reach Shift strongly pulls the other fingertips off their alignment with home row. Since the Shift modifier key must be reached so frequently to capitalize words, even typists using mechanical keyboards have long complained about the awkward pinky twist and ulnar deviation at the wrist necessary to hold it down. Accurately, hitting the Shift keys becomes, if anything, more awkward on a relatively smooth surface that does not give like a mechanical key.
In the related ergonomic and chord keyboard art exemplified by FIG. 2 modifier keys such as Shift, Ctrl, and Alt are often allocated to the thumbs (e.g. U.S. Pat. No. 5,642,108 to Gophert et al. and U.S. Pat. No. 5,689,253 to Hargreaves et al.) or to palm presses, as in U.S. Pat. No. 5,017,030 to Crews. However, for a multi-touch surface, reaching the thumb for modifier keys poses the same drift exacerbation problems as reaching by the pinky, and palm touches should be ignored to encourage hand resting. Thus there exists a need in the multi-touch and chord keying art for alternative methods to activate modifier keys without drawing any fingers away from the row.